The present invention relates to a semiconductor device called "power module", which houses a circuit board having semiconductor elements thereon in an insulative case frame, and more specifically to a structure for installing a lead pin block on which many lead pins are formed.
FIG. 4 is a top plan view showing a structure of a conventional semiconductor device called "power module" or "intelligent power module". And, FIG. 5 is a cross sectional view taken along line 5--5 in FIG. 4.
As shown in these figures, the semiconductor device has an insulative case frame 10 having a frame portion 12. A radiator base plate or metal plate 20 is bonded with an adhesive to a first opening step 14 formed on a first side of the frame portion 12 to close a first opening of the case frame 10. Circuit boards 30, 31, i.e. ceramic boards, are bonded with a solder and so on to the inside face of the radiator base plate 20. Lead frames 40 through 45 are connected at the inner lead ends A thereof to a thick film wiring formed on the circuit board 30. A lead Din block 70 with lead pins P1 through P16 standing thereon is fixed to the frame portion 12 of the insulative case frame 10. The ends B of inner leads of the respective lead pins P1 through P16 are connected to the thick film wiring formed on the circuit board 31. A gel resin sealant 50, e.g. silicone resin, is filled in an inner space of the case frame 10 to immerse or cover the circuit board 30, the inner leads of the lead frames 40 through 45 and the inner leads of the lead pins P1 through P16. An insulative cover plate 60 is bonded with an adhesive to a second opening step 18 formed on a second side of the frame portion 12 to close the second opening of the case frame 10.
Semiconductor elements or chips 32, 34, such as power transistors, IGBTs (conductivity-modulation-type transistors), diodes, thyristors, and so on are mounted on the circuit boards 30, 31. The inner lead ends A of the lead frames 40 through 45 are bonded with a solder and so on to the land portions of the thick film wiring of the circuit board 30, and connected through bonding wires 32a, 34a to the corresponding semiconductor elements 32, 34.
The lead frames 40 through 45 are fixed to the frame portion 12 by insert molding, and terminal washers 40a through 45a at the frame portion 12 are connected with terminal screws (not shown) for outer connection.
FIG. 6 is an exploded perspective view showing a lead pin block and its installation structure. Referring now to FIG. 6, the lead pin block 70 is molded by an insert molding separately from the insulative case frame 10. The lead pin block 70 includes a base 71 on which the lead pins P1 through P16 are standing, a step 72, a coupling claw (not shown) formed on the other side opposite to the face that the step 72 is formed, and guide pins G1, G2. The upper face of the step 72 is positioned at the same height as the upper face of the second opening step 18 when the step 72 is inserted into slots 12a formed on the inner face of the frame portion 12 of the insulative case frame 10, so as to accept the insulative cover plate 60. The coupling claw couples with a wedge-shaped coupling claw 12b formed on the inner face of the frame portion 12. The guide pins G1, G2 are inserted into respective quiche holes formed on a female connector (not shown) for the lead pins P1 through P16. A pair of support pins 12c, which sustain the inserted lead pin block 70 at the predetermined height, is formed on the inner face of the frame portion 12.
The lead pin block 70 is formed by molding separately from the insulative case frame 10 for reducing the volume of the resin mold to further reduce the influence of the sink and so on of the resin. By this measure, the precision of the pitch between the lead pins and the verticalness of the lead pins P1 through P16 are improved, and therefore, the production yield of the semiconductor device is improved.
The lead pin block 70 is installed on the insulative case frame 10 tightly enough not to come out easily by inserting the lead pin block 70 into the slots 12a and coupling the coupling claw 12b of the frame portion 12 with the coupling claw of the lead pin block 70. Thereafter, as shown in FIG. 7, the gel resin sealant 50, i.e. silicone resin, is filled in the insulative case frame 10, and then closed with the insulative cover plate 60 bonded with an adhesive to the second opening step 18 of the insulative case frame 10 and the step 72 of the lead pin block 70.
The above described structure for installing the lead pin block 70 on the semiconductor module has following drawbacks.
The gel resin sealant 50, i.e. silicone resin, is heated to cause heat expansion due to heating for bonding the insulative cover plate 60 to the insulative case frame 10 or heat generated from the power elements, covered by the gel resin sealant 50, of the operating semiconductor module. The expanding gel resin sealant 50 spreads out through an insertion gap G between the base 71 of the lead pin block 70 and the inner face of the frame portion 12, or lifts up the insulative cover plate 60.
Also, since the lead pins P1 through P16 are extremely fine square rods less than 1 mm in width, the lead pins are easily bent by the unwanted contact and so on during packaging or transporting of the semiconductor module. And, the resin guide pins G1, G2 are easily broken.
In view of the foregoing, it is an object of the invention to provide a semiconductor device for installing a lead pin block that prevents the gel resin sealant from spreading out through the insertion gap between the base of the lead pin block and the inner face of the frame portion.
It is another object of the invention to provide a semiconductor device with a protective structure that prevents the lead pins and guide pins from bending or breaking during transporting and so on of the semiconductor device.